Exothermic: Describes a process which emits energy.
Endothermic: Describes a process which absorbs energy.
Enthalpy Change of Combustion: The process when one mole of a compound is completely burnt in excess oxygen.
Enthalpy Change of Formation: The process when one mole of a compound is formed from it's elements in their standard states.
Enthalpy Change of Reaction: The energy change at a constant pressure and a stated temperature for a process in which a specified amount of reactants are converted into products.
Entropy: The measure of the number of ways particles can be arranged.
Catalyst: A substance which changes the rate of a chemical reaction without undergoing any change itself.
Energy Changes and Chemical Reactions
- Exothermic reactions give out heat and have negative enthalpy changes.
- When a reaction gives out heat the chemical reactants are losing energy so the products end up with less energy than what the reactants had.
- Endothermic reactions take in heat and have positive enthalpy changes.
- In an endothermic reaction the reactants take in energy from their surroundings so the products end up with more energy than what the reactants had.